The abuse of illicit drugs such as cocaine and MDMA inflicts tremendous damage on society. According to the Department of Health and Human Services, approximately 35 million persons 12 or older use an illicit drug within each year, and more than 3.8 million were dependent on or abusers of illicit drugs in 2003. Although drug prevention advertisements have been used for decades and are an important part of anti-drug policy, there is considerable controversy over how effective these ads are at deterring drug use, and there is a growing need for the development of new innovative assessment tools. We propose that functional magnetic resonance imaging (fMRI) can provide insights into the effectiveness of substance abuse prevention messages, and can provide a useful complement to existing explicit and implicit measures of ad effectiveness. We will combine methods from marketing research with fMRI, galvanic skin response, and eye movement data, to determine engagement in and effectiveness of anti-drug ads. We propose using a novel inter-subject correlation (ISC) analysis that we have recently shown to be a powerful tool for exploring the function and organization of the human brain during natural viewing of complex stimuli (e.g., films in our previous research;advertisements in the current application). The proposed experiments will provide a detailed characterization of the activation patterns associated with engagement in the ads, distinguish between the engagement level and the effectiveness of each ad, and identify interventions for enhancing the effectiveness of prevention messages. Moreover, the proposed research provides an opportunity for characterizing correlations between individual differences in personality traits with individual differences in neural processing. Finally, the proposed research is a platform for studying the basic neural processes underlying engagement. The abuse of illicit drugs such as cocaine and MDMA inflicts tremendous damage on society. The proposed research plan is aimed at characterizing the neural correlates of the engagement level and effectiveness of different substance abuse prevention messages. We propose to combine methods from marketing research neuroscience research to develop new tools for assessing the effectiveness of different prevention messages. Such tools have the potential to ensure that prevention messages are effective and that taxpayers'dollars are efficiently used.